Seattle’s mayoral race is shaping up as a four-person contest between Mayor Mike McGinn and three challengers jostling to see who will make it past the Aug. 6 primary.

Judged by recent polling and endorsements, McGinn’s top opponents are state Sen. Ed Murray, City Councilmember Bruce Harrell and former Councilmember Peter Steinbrueck.

With just seven weeks to go until ballots are mailed, none of the candidates has seized front-runner status in a race that has so far centered more on critiques of McGinn’s leadership style than major policy disagreements.

In a recent KING-TV poll of 522 likely voters, McGinn led with 22 percent support. Steinbrueck placed second with 17 percent, closely followed by Murray at 15 percent and Harrell at 12 percent. The biggest group of voters — 23 percent — remains undecided. None of the other five candidates received more than 4 percent.

The four leaders also came away with a split score card in a round of Democratic legislative-district endorsements over the past few weeks — another traditional early test for Seattle candidates.

“Saying this race is anything but gelatinous at this point would be an overstatement,” said Michael Grossman, a Seattle-based political consultant, who called the support for McGinn’s rivals “soft.”

Because McGinn is better known, his core of supporters is likely more solid, Grossman noted. But the mayor’s lackluster numbers look dangerously similar to those of McGinn’s predecessor, Greg Nickels, who failed to get through the 2009 primary. “It looks like McGinn is in the same lifeboat,” he said.

McGinn’s prospects might have worsened with the surprise departure of City Councilman Tim Burgess from the race. Burgess had been the leading mayoral fundraiser but struggled to distinguish himself from other challengers and withdrew hours before the May 17 filing deadline. That leaves one less prominent challenger to divide the anti-incumbent primary vote.

Throughout the early campaign, McGinn’s opponents have spent much of their time portraying him as a combative and divisive figure who is holding Seattle back. But differences on major issues are harder to spot.

“It seems like we are all in violent agreement” on most subjects, Harrell said to members of the 36th District Democrats at Seattle’s Labor Temple last week.

But each candidate has tried to flavor his appeal in subtly different ways to attract the 25 to 30 percent of votes that will likely be needed to advance past the primary.

McGinn, the former environmental activist and attorney who had never held public office before being elected mayor in 2009, says despite what his critics would have you believe, things are going pretty well in Seattle.

“Jobs are up, crime is down, the budget is balanced. Now they all want my job,” he said.

McGinn notes he’s faced protests, a snowstorm and even a garbage strike during his first term. His supporters say the bike-riding mayor represents Seattle’s values and frequently talk up a local union endorsement calling him “the most progressive mayor in America.”

But McGinn struggled in the recent set of Democratic district-endorsement meetings, landing just one: a shared endorsement with Harrell from the 37th District Democrats of Southeast Seattle.

Murray, the state Senate Democratic leader who has represented Seattle’s 43rd District for more than a decade, plays up his experience working in the ideologically diverse environment of the Legislature.

Citing squabbling among Seattle leaders, Murray said, “We’re a group of liberals who agree basically on what we want to do, but can’t seem to get together on it.”

He said his skills in Olympia, chairing budget and transportation committees and working with Republicans and Democrats, would give him an edge in working cooperatively with other regional leaders.

Murray also is riding perhaps his crowning legislative achievement, last year’s legalization of gay marriage, which was upheld at the ballot in November. If elected he’d be Seattle’s first openly gay mayor.

Steinbrueck, the former city-council member, disagrees with his rivals that there is no significant difference among them on issues in the mayoral contest. “I don’t think we agree on the future of the city,” he said.

An architect and civic activist before serving three terms on the council, Steinbrueck is staking out a position as a defender of neighborhoods against unfettered development.

He argues that McGinn and the City Council were irresponsible in the recent approval of dramatically taller buildings in South Lake Union without demanding enough affordable housing and other concessions in return.

Steinbrueck also earned the ire of NBA fans, but the support of maritime unions, by loudly opposing plans to build a new arena in the Sodo neighborhood.

Harrell, who was elected to the City Council in 2007, said his “success story” biography sets him apart.

He grew up in Seattle’s Central District in the 1960s to become a Washington Huskies football star, corporate attorney and community leader, while many kids he knew wound up in prison.

On the campaign trail, Harrell says he is the one calling attention to “social-justice” issues, including police reform and disparities among rich and poor parts of the city.

“What Seattle needs is someone who can create one Seattle. We need someone who can talk to Steve Ballmer on the same day I am talking to a kid who is behind bars,” Harrell said.

If there is a longshot in the race, it could be businessman Charlie Staadecker, who has shown prowess on at least one front. He has raised more than $150,000, making him one of the top fundraisers among the candidates.

But Staadecker, who founded and runs a real-estate company, has barely registered in polls and failed to obtain a single endorsement from any of the Democratic district groups.

The amiable, bow-tie-wearing Staadecker contends he’d do better if he got more media attention.

He said he’s more politically moderate than his “colleagues” (as he calls his rivals) and would better promote tourism and business. “I see voters looking for somebody who is balanced and deals in common sense,” he said.